Digital signal-processing (DSP) tools, such as Ptolemy, LabView and iConnect, allow application developers to assemble reactive systems by connecting pre-defined components in generalised dataflow graphs and by hierarchically building new components by encapsulating sub-graphs. We follow the literature in calling this approach dataflow-oriented development. Our previous work has shown how a new process calculus, uniting ideas from previous systems within a compositional theory, can be formally shown to capture the properties of such systems. This paper first re-casts the graphical dataflow-oriented style of design into an underlying textual architecture design language (ADL) and then shows how the previous modelling approach can be seen as a system of process-algebraic behavioural types for such a language, so that type-checking is the mechanism used to statically diagnose the reactivity of applications. We show how both the existing notion of behavioural equivalence and a new behavioural pre-order are involved in this judgement.